Field of the Invention
The invention relates to the field of optical signal and data transmission, especially in multiprocessor systems, for which increased use of so-called optical bus systems may be expected in the forseeable future. In principle, a data bus is understood to mean the use of one common signal path by a plurality of participants. To that end, the signal path has branches for signal output and/or signal input. This is no problem in electrical signal lines or bus systems, because of the electrical conductor properties. However, optical wave guide branching--especially in data transmission systems with a large number of parallel data lines--is a demanding technological problem.
The invention pertains to a branching optical wave guide configuration, having at least one continuous optical wave guide. The latter has a light-guiding core which is disposed on a substrate. At least one branching optical wave guide is disposed at an angle to the continuous optical wave guide and its coupling end face faces toward the continuous optical wave guide. At least one reflective face effects a light transfer between the continuous optical wave guide and the branching optical wave guide. Similarly, the invention also relates to a branching optical wave guide array. The term light-guiding core in the context of the present invention is understood to mean the core region, used for optical wave guidance, of an optical wave guide. In practical embodiment, various combinations of materials for the core and the cladding jacket are possible. Due to the different indices of refraction, the materials bring about light guidance. The jacket may for instance be formed of a separate material with a lower index of refraction, but may also be formed by the substrate or at exposed faces by the ambient air.
An optical wave guide configuration of this generic type is known in principle from the paper entitled "4.times.16 Polymer Fiber Optical Array Couplers" by Yao Li, Ting Wang and K. Fasanella in 8 IEEE PHOTONICS TECHNOLOGY LETTERS No. 12, Dec. 1996. That prior art optical wave guide configuration is a 4.times.16 beam splitter, using polymer optical fibers (POFs) with four continuous optical wave guides. Each of the continuous optical wave guides is defined by a defined removal of material such that in each case some of the light guided in it is transferred into one or all of the four branching optical wave guides each assigned to it. Specifically, the prior art wave guide configuration has three plastic plates for this purpose. The total of 16 branching optical wave guides are fixed in through bores of a base plate. The surface of the base plate is formed with four grooves for receiving the four continuous optical wave guides that are at right angles to the branching optical wave guides. The coupling end faces of the branching optical wave guides are each in partial-surface contact with the jacket face of the respective continuous optical wave guides assigned to them. An upper plate likewise has four grooves for fixing the continuous optical wave guides and also has 16 larger through bores, through which cutting blades can be placed in contact with the continuous optical wave guides. The continuous optical wave guides are fixed between the base plate and the upper plate by screw forces and are cut in at an angle of 45.degree. from their jacket face with the aid of a cutting tool delivered through the through bores. Next, by one further cut each, an approximately cylindrical hoof shaped region is cut out of the optical wave guide material. The cut face oriented obliquely to the longitudinal axis of the optical wave guide forms a reflective face.
That prior art optical wave guide configuration requires not only many individual parts that must be finished and mounted separately but also highly precise cutouts of material from the continuous optical wave guides. Producing such an optical wave guide configuration is therefore very complicated and expensive, and because the orientation and quality of the reflective faces depends on the course of the cuts, optimal optical properties cannot always be guaranteed. Moreover, the packing density and the division in the continuous optical wave guides are structurally restricted.